Method and device for printing wherein a hydrophilic layer is produced and structured

ABSTRACT

In a method and device to generate a print image on a carrier material, a hydrophilic layer with a molecular layer thickness is generated at a surface of a print carrier usable for printing, a surfactant layer being applied on the surface of the print carrier to generate the hydrophilic layer. As a structuring process, hydrophilic regions and hydrophobic regions are generated corresponding to the structure of the print image to be printed. On the surface of the print carrier, a fountain solution layer is applied whereby the fountain solution layer forms on the hydrophilic regions such that ink-attracting regions and ink-repelling regions are created corresponding to the print image structure. Ink that adheres to the ink-attracting regions and is not absorbed by the ink-repelling regions is applied on the surface. The applied ink is transferred onto the carrier material. Before a new structuring process, the surface of the print carrier is cleaned.

BACKGROUND

The method and device relate to generating a print image on a carriermaterial. On the surface of the print carrier ink-attracting andink-repelling regions are generated corresponding to the structure ofthe print image to be generated. The ink-repelling regions are providedwith a layer from an ink-repelling medium. Ink that adheres to theink-attracting regions and is not accepted by the ink-repelling regionsis applied on the surface of the print carrier. The ink distributed onthe surface is printed on the carrier material.

In the prior art, offset printing methods operating without water areknown whose non-printing regions are fat-repelling and therefore acceptno printing ink. In contrast, the printed regions are fat-attracting andaccept the fat-containing printing ink. Ink-attracting and ink-repellingregions are distributed on the printing plate corresponding to thestructure of the print image to be printed. The printing plate can beused for a plurality of transfer printing events. A new plate withink-attracting and ink-repelling regions must be generated for eachprint image.

From U.S. Pat. No. 5,379,698, a method (called the Direct ImagingMethod) is known in which a printer's copy is created in the printingdevice via selective burning-off of the silicon cover layer on amultilayer, silicon-coated film. The silicon-free locations are theink-attracting regions that accept printing ink during the printingevent. It requires a new film for each new print image.

In the standard offset method operating with water, hydrophobic andhydrophilic regions are generated on the surface of the print carriercorresponding to the structure of the print image to be printed. Beforethe application of the ink, a thin moisture film that wets thehydrophilic region of the print carrier is first applied onto the printcarrier using application rollers or spray devices. The ink rollersubsequently transfers ink onto the surface of the print carrier that,however, exclusively wets the regions not covered with the moisturefilm. The ink is finally transferred onto the carrier material after theinking.

In the known offset printing method, multilayer, process-lessthermoprinting plates can be used as print carriers (compare, forexample, WO00/16988). On the surface of the print carrier, a hydrophobiclayer is removed via partial burn-off and a hydrophilic layer isuncovered, corresponding to the structures of the print image to beprinted. The hydrophilic layer can be wetted with an ink-repellingfountain solution. The hydrophobic regions are ink-accepting and canaccept printing ink during the print event. A new printing plate must beused to create a new print image.

Furthermore, a method is known from U.S. Pat. No. 6,016,750 in which anink-attracting substance is separated from a film by means of athermotransfer method, transferred to the hydrophilic surface of theprint carrier and solidified in a fixing process. In the printingprocess, the hydrophilic regions remaining free are wetted with anink-repelling fountain solution. The ink is subsequently applied on thesurface of the print carrier, the ink, however, bonding only on theregions provided with the ink-attracting substance. The inked printimage is then transferred onto the carrier material. A new film with theink-attracting substance is necessary for the creation of a new printimage.

In the standard offset method or surface printing method, the wetting ofthe printing plate with the ink-repelling fountain solution is achievedvia a specific roughening and structuring of the plate surface. Thesurface increase and porosity thereby created generates microcapillariesand leads to an increase of the effective surface energy and thus to agood wetting or spreading of the fountain solution. As furthertechniques, in offset printing wetting-aiding substances are added tothe fountain solution. These decrease the surface tension of thefountain solution, which in turn leads to an improved wetting of thesurface of the print carrier. The literature Teschner H.: Offsettechnik,5th edition, Fellbach, Fachschriften-Verlag 1983, pg. 193-202 and pg.350 is referenced in this context.

From U.S. Pat. No. 5,067,404, a printing method is known in which afountain solution is applied to the surface of the print format. Thefountain solution is vaporized via selective application of radiantenergy in image regions. The water-free regions later form theink-bearing regions that are directed to a developing unit and are inkedby means of an ink vapor. Energy-intensive partial vaporizationprocesses are necessary to generate the structured fountain solutionfilm.

Furthermore, the patent documents WO 97/36746 and WO 98/32608 arereferenced. In the method specified in WO 97/36746, the fountainsolution is generated via vaporization of a discrete water volume thatcondenses on the surface of the print carrier. According to WO 98/32608and the U.S. Pat. No. 6,295,928 derived therefrom, a continuous ice filmis applied and structured. In both cases, local high thermal energy mustbe applied for structuring. The aforementioned documents U.S. Pat. No.5,067,404, WO 98/32608 (U.S. Pat. No. 6,295,928) and WO 97/36746 by thesame applicant are herewith included by reference in the disclosurescope of the present patent application.

From DE-A-10132204 (not published) by the same applicant, a CTP method(Computer-To-Press method) is specified whereby multiple structuringprocesses can be implemented on the same surface of the print carrier.The surface of a print carrier is coated with an ink-repelling orink-attracting layer. In a structuring process, ink-attracting regionsand ink-repelling regions are generated corresponding to the structureof the print image to be printed. The ink-attracting regions are theninked with ink. Before a new structuring process, the surface of theprint carrier is cleaned and re-coated with an ink-repelling orink-attracting layer. A fountain solution layer or an ice layer is usedas a layer. This patent document DE-A-10 132 204 is herewith included byreference in the disclosure content of the present patent application.

SUMMARY

It is an object to specify a printing method and a print device that isdesigned simply for digital printing with alternating print images onthe same print carrier and that enables a high print quality.

In a method and device to generate a print image on a carrier material,a hydrophilic layer with a molecular layer thickness is generated on asurface of a print carrier usable for printing, a surfactant layer beingapplied on the surface of the print carrier to generate the hydrophiliclayer. As a structuring process, hydrophilic regions and hydrophobicregions are generated corresponding to the structure of the print imageto be printed. At the surface of the print carrier, a fountain solutionlayer is applied whereby the fountain solution layer forms on thehydrophilic regions such that ink-attracting regions and ink-repellingregions are created corresponding to the print image structure. Ink thatadheres to the ink-attracting regions and is not absorbed by theink-repelling regions is applied on the surface. The applied ink istransferred onto the carrier material. Before a new structuring process,the surface of the print carrier is cleaned.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a principle representation of a print device in which asurfactant layer is applied;

FIG. 2 shows schematically, a cross-section through the print carrierbefore and after the structuring by a laser beam;

FIG. 3 is an exemplary embodiment in which a hydrophilized layer isstructured;

FIG. 4 is an exemplary embodiment in which an applied hydrophilic layeris structured;

FIG. 5 is a schematic cross-section through the print carrier before andafter the structuring of the hydrophilic layer;

FIG. 6 is an exemplary embodiment in which the hydrophilization occursvia a corona discharge;

FIG. 7 is a cross-section through an insulated electrode;

FIG. 8 is an arrangement given a plastic print carrier;

FIG. 9 is an example for an indirect corona discharge; and

FIG. 10 is a print device with a regulation of the fountain solutionlayer thickness.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the preferred embodimentillustrated in the drawings and specific language will be used todescribe the same. It will nevertheless be understood that no limitationof the scope of the invention is thereby intended, such alterations andfurther modifications in the illustrated device, and/or method, and suchfurther applications of the principles of the invention as illustratedtherein being contemplated as would normally occur now or in the futureto one skilled in the art to which the invention relates.

According to the preferred embodiments, a hydrophilic layer is generatedin a molecular layer thickness on the surface of a print carrier usablefor printing. Before the application of a fountain solution layer thehydrophilic layer is influenced in a structuring process such thathydrophilic regions and hydrophobic regions are generated correspondingto the structure of the print image to be printed. Given subsequentapplication of a fountain solution layer, a fountain solution filmattaches only to the hydrophilic regions, such that ink-attractingregions and ink-repelling regions are created corresponding to theeffected structuring. After the transfer printing and a cleaning, thissame surface of the print carrier can be re-structured and if necessaryprovided with a modified print image.

The expenditure in the structuring is reduced by the preferredembodiment. The necessary energy in order to structure a hydrophiliclayer is reduced relative to the structuring of a fountain solutionlayer. The necessary hardware expenditure is reduced accordingly.

According to a further aspect of the preferred embodiment, a printdevice is specified via which the cited method can be realized.

It is to be noted that the term ink-repelling or ink-accepting layeroccurs frequently in the further specification. This layer is adapted tothe ink to be applied. For example, given a water-containing fountainsolution layer and an oil-containing ink, the fountain solution layer isink-repelling. However, if the ink is water-containing, this fountainsolution layer is ink-attracting. In practice, oil-containing inks arepredominantly used, such that a water-containing fountain solution layeris ink-repelling.

In FIG. 1, a principle representation of a print device is shown that isdesigned similar to how it is specified in U.S. Pat. No. 5,067,404 bythe same applicant. A print carrier 10, in the present case a continuousband, is directed through a pre-treatment device 12 that comprises ascoop roller 14 and an application roller 16. The scoop roller 14 dipsinto a fluid contained in a reservoir 13, the fluid containing awetting-aiding substance. This substance, which comprises surfactants,is applied in a molecular layer thickness on the surface of the printcarrier 10 via the application roller 16. The layer thickness istypically smaller than 0.1 μm. The surface of the print carrier 10 isthen directed in arrow direction P1 to a dampening system 18 that, via ascoop roller 20 and an application roller 22, applies an ink-repellingor ink-attracting fountain solution, for example water, from fountainsolution reservoir 24 onto the surface of the print carrier 10. Inprinciple, other fountain solution than water can also be used. Theapplication of the fountain solution layer can also occur via othermethods, for example via dampening or spraying. The print-active surfaceof the print carrier 10 is completely provided with this fountainsolution layer. The fountain solution layer typically has a layerthickness smaller than 1 μm.

The generally ink-repelling fountain solution layer is subsequentlystructured via an image generation device 26. In the present case, alaser beam 28 is used for this. In this structuring process,ink-attracting regions and ink-repelling regions are generatedcorresponding to the structure of the print image to be printed. Thestructured fountain solution layer subsequently arrives at an inkingsystem 30 which transfers ink from a reservoir 38 to the surface of theprint carrier 10 with the aid of the rollers 32, 34, 36. Theoil-containing ink attaches at regions without water-containing fountainsolution. It is to be noted that the ink can also be transferred ontothe surface of the print carrier 10 via spraying, scraping orcondensation.

Given further transport of the print carrier 10, a transfer printingonto a carrier material 40 (in general a paper web) occurs. For transferprinting, the carrier material 40 is directed through between tworollers 42, 44. In the transfer printing process, a rubber blanketcylinder (not shown) and further intermediate cylinders that effect anink division as this is known from the field of offset printing methodscan be inserted between the roller 42 and the print carrier 10.

Given further transport of the print carrier 10, the surface of theprint carrier 10 is cleaned in a cleaning station 46. The ink residuesas well as the residues of the surfactant layer are hereby removed. Thecleaning station 46 comprises a brush 48 and a wiping lip 50 which arebrought into contact with the surface of the print carrier 10.Furthermore, the cleaning can be supported via use of ultrasound, highpressure liquid and/or vapor. The cleaning can also occur using cleaningfluids and/or solvents.

A new application of the wetting-aiding substance, for example asurfactant application, and a fountain solution application as well as arestructuring can subsequently occur. In this manner, a new print imagecan be printed given every revolution of the print carrier 10. However,it is also possible to print the same print image multiple times. Thecleaning device 46, the device 12 and the device 26 are then switched toinactive. The print image still present in ink residues is then re-inkedand transfer-printed by the inking system 30. Given this operating type,a plurality of identical print images can thus be printed.

FIG. 2 schematically shows a cross-section through the print carrier 10before and after the structuring with the aid of the laser beam 28.According to the preferred embodiment, the wetting via the applicationof a wetting-aiding substance is conveyed onto the print carrier surface10. This occurs within the print cycle before the application of theink-repelling fountain solution. The wetting-aiding substance can beapplied on the surface (dependent on its physical and chemicalproperties) as an extremely thin layer of a few molecule layers,preferably smaller than 0.1 μm. This layer is sufficient in order topromote the wetting with the ink-repelling fountain solution on its freesurface, such that this can in turn be applied as a very thin layer 54,preferably smaller than 1 μm. The continuing print process is notimpaired by the small quantity of the wetting-aiding substance, in thiscase a surfactant layer 52. It can easily be removed again via thecleaning process integrated into the print cycle.

Advantages primarily result in the field of surface printing or offsetprinting, meaning a surface printing method or offset printing methodwith alternating print information from print cycle to print cycle. Viathe wetting-aiding layer 52, the otherwise typical roughened, porousprinting plate surface can be foregone. Instead of this, a smoothsurface of the print carrier 10 is possible that is to be cleaned withclearly lesser effort. A faster and more stable cleaning event isindispensable for such a digital surface printing method or offsetprinting method and a decisive factor for its effectiveness. The surfaceof the print carrier 10 accordingly has a roughness that is smaller thanthe roughness used in the standard offset printing method. The averagesurface roughness R_(z) is typically smaller than 10 μm, preferablysmaller than 5 μm. Expressed as an average roughness value R_(a), theroughness value is in a range smaller than 2 μm, preferably smaller than1 μm.

A change in the molecular or atomic structure of the material of theprint carrier as well as a wetting-aiding layer permanently and firmlyanchored with the surface of the print carrier is not necessary. Theadditionally applied wetting-aiding substance (for example thesurfactant layer 52) proposed here already deploys its wetting-aidingeffect given the smallest quantities. Its influence on the properties ofthe print carrier 10 in all regards is accordingly negligible. A furtheradvantage results from the now-possible abandonment of the typicallypresent wetting-aiding additives in fountain solutions in offsetprinting.

According to FIG. 2, the fountain solution layer 54 and the surfactantlayer 52 are removed via the laser beam 28 corresponding to the requiredimage structure. These regions are then inked with ink by the inkingsystem 30. The cleaning is eased due to the very smooth surface of theprint carrier 10, whereby the surfactant layer 52 is completely removedagain. Furthermore, the wear of the surface of the print carrier 10 isreduced.

In the following Figures, functionally identical elements are designatedidentically. FIGS. 3, 4 and 5 show a further exemplary embodiment of theinvention. In FIG. 3, in contrast to the exemplary embodiment accordingto FIG. 1, before the application of the ink-repelling or ink-attractinglayer on the usable surface of the print carrier a structuring of ahydrophilic layer ensues with a molecular layer thickness. In thepresent example, a vapor device 60 is used that charges the surface ofthe print carrier 10 with hot water vapor. The print carrier 10 isprovided with an SiO2 coating on its surface. After the vapor treatment,the print carrier 10 is dried via a suction device 62. The hot watervapor generates a hydrophilic molecule structure, for example SiOH, onthe outer surface.

After the subsequent structuring via the structuring device 26 by meansof laser radiation 28, hydrophilic and hydrophobic regions are createdcorresponding to the structure of the print image to be printed. Via thedownstream dampening system 18, the entire usable surface of the printcarrier 10 is contacted with a fountain solution layer, whereby thefountain solution attaches only to the hydrophilic regions, such thatink-attracting regions and ink-repelling regions are createdcorresponding to the aforementioned structuring. An ink application viathe inking system 30 subsequently occurs, whereby the oil-containing inkattaches to regions without water-containing fountain solution. Thetransfer printing of the print image onto the carrier material 40subsequently occurs.

After the further transport of the print carrier 10, its surface iscleaned in a cleaning station 46. The ink residues and the residues of apossible wetting-aiding substance are removed. A new structuring processcan subsequently occur.

In the present example according to FIG. 3, the hydrophilic layer on thesurface of the print carrier 10 is structured corresponding to the printimage. The hydrophilic layer is extremely thin and is only a fewnanometers, typically smaller than 4 nm. It can therefore by structuredwith very low energy expenditure during a print cycle, whereby thehydrophilic molecule layer disappears. The fountain solutionapplication, which generates a fountain solution film only on thenon-hydrophilic regions, subsequently occurs. Inking and transferprinting occurs according to the specified known principles of surfaceprinting or offset printing. After the cleaning, in which thehydrophilic layer can also be removed (however does not absolutely haveto be removed) in addition to the ink residues, the print cycle canbegin anew. The hydrophilic layer is regenerated or reapplied and thehydrophilic layer is subsequently structured corresponding to the newimage data.

In the example according to FIG. 3, the generation of the hydrophiliclayer occurs via activation of the surface of the print carrier and viaa suitable change of the external molecular surface structure. Forexample, this can be enabled via the use of chemical activators,reactive gases and/or a suitable energy supply. In addition to the useof water vapor as in the example according to FIG. 3, a hydrophilic SiOHstructure can be designed on the surface via the effect of hot water andvia alkaline solutions (such as, for example, NaOH). For this, the printcarrier is to be provided with an SiO2 coating. It is also possible thatthe print carrier passes through an activator bath in order to generatea hydrophilization of the surface. The application of an activator via ajet system is also possible. A further possibility is to generate thehydrophilic layer via firing the surface of the print carrier 10.Wetting-aiding surface structures are also hereby created in a molecularlayer thickness.

An advantageous arrangement is the combination of the hydrophilizationwith the cleaning. Thus, for example, both the cleaning and thehydrophilizing effect of a hot water jet or a hot water vapor jet can beused. The cleaning and the generation of the hydrophilic layer are thenimplemented in a single process step.

A further variant is shown in FIG. 4. A wetting-aiding substance ishereby applied to the surface of the print carrier to generate thehydrophilic layer. For example, the pre-treatment device 12 specified inthe embodiment according to FIG. 1 can be used. With the aid of thescoop roller 14 and the application roller 16, a fluid from thereservoir 13 can be applied that comprises a wetting-aiding substance,for example a surfactant, in a molecular layer thickness. Here as wellthe layer thickness is typically smaller than 0.1 μm. Alcohols are alsoconsidered as a further wetting-aiding substance. The application canalternatively ensue via scraping on, spraying on and vapor deposition.

Due to the very thin hydrophilic layer in molecular layer thickness, thepartial removal of this hydrophilic layer can ensue via local thermalenergy supply. The energy expenditure can be low due to the low layerthickness. In addition to the laser radiation 28 used in FIGS. 3 and 4,laser diodes, LEDs, LED combs or heating elements can also be used.

In the example according to FIGS. 3 and 4, a restructuring can alsooccur per cycle of the print carrier 10, whereby a new print image isprinted per cycle. However, it is also possible (as in the exampleaccording to FIG. 1) to print the same print image multiple times,whereby the existing print image is re-inked and transfer-printed by theinking system 30. The devices for the restructuring are then switched toinactive.

FIG. 5 shows a cross-section through the print carrier 10 before andafter the structuring via the laser beam 28 for the example according toFIG. 4. The surface of the print carrier 10 is very smooth, as this isalso the case in the preceding examples. The thin surfactant layer 52 isstructured by the laser beam 28, meaning hydrophilic regions 68 andhydrophobic layers 64 are generated. A thin, water-containing moisturefilm is applied by the dampening system 18 only on the hydrophilicregions. The regions 64 are then inked by the inking system 30 with anoil-containing ink that is repelled by the fountain solution 54 in thearea of the hydrophilic regions 68.

The subsequent exemplary embodiments according to FIGS. 6 through 9describe the hydrophilization of the surface of the print carrier 10 viacharging with free ions. These exemplary embodiments can also becombined with the example according to FIG. 3.

In order to ensure a good wetting with the generally ink-repellingfountain solution film, the surface energy of the print carrier 10 mustbe at least as high as the surface tension of the fountain solutionfilm. This means that the value of the contact angle between the surfaceof the print carrier 10 and the fountain solution must assume a valuebelow 90°. In practice, it is necessary that a contact of angle of <25°has to be achieved in order to generate the necessary liquid film with athickness of approximately 1 μm. This places a high demand on thesurface energy of the print carrier primarily when one considers theextremely high surface tension value of water, namely 72 mN/M, as abasis of the ink-repelling fountain solution. Plastic print carriers ormetallic print carriers can not achieve this without further measuressuch as, for example, roughening, application of surfactants, generationof microcapillaries, etc. For example, the contact angle of water topolyimide or polycarbonate is approximately 75°. Even metal surfacesthat, in their purest form, exhibit very high surface energies and thusthe smallest contact angles show relatively hydrophobic behavior undernormal environmental conditions. This is substantially connected withthe oxidation layer acting on metal surfaces that always forms undernormal conditions. Even the slightest impurities have a negative effectin this context for the desired surface energy. Contact angles of over700 are herewith frequently to be encountered in practice.

In the example according to FIG. 6, a corona treatment of the surface ofthe print carrier 10 is effected for hydrophilization. A high-voltagegenerator 70 generates an alternating voltage in the range of 10 to 30kV, preferably in the range of 15 to 20 kV, at a frequency of 10 to 40kHz, preferably in the range of 15 to 25 kHz. An output connection ofthe high-voltage generator 70 is connected with an insulated electrode72. The other output connection is, in the present case of a metallicprint carrier 10, attached to a loop contact 74 that is connected withthe print carrier 10.

The relatively high voltage at the electrode 72 leads to ionization ofthe air. A corona discharge is created, whereby the surface of the printcarrier 10 is bombarded with free ions. Given a plastic surface, inaddition to a cleaning effect in which organic impurities such as fat,oil, wax, etc. are typically removed, this leads to the creation of freeradicals on the surface that form strongly hydrophilic functional groupsin connection with oxygen. They are hereby primarily carbonyl groups(—C═O—), carboxyl groups (HOOC—), hydroperoxide groups (HOO—) andhydroxyl groups (HO—). Given metallic print carriers, the cleaningeffect is in the foreground, whereby an increase of the surface energy,and thus a reactivation of the hydrophilic properties of metals, isachieved via degreasing of the surface and removal of the oxide layer.In this manner, contact angles to water of under 20° can be achievedwith plastic surfaces and with metal surfaces. The corona treatmentmodifies the physical surface properties of the carrier beforehand,however not its mechanical properties. No visible changes aredetectable, for example with a scanning electron microscope. Viavariation of the height of the voltage or the frequency of thehigh-voltage generator, the effect on the surface of the print carrier10 can be influenced and attuned to the respective carrier material. Thehydrophilization can be improved via supply of process gases, preferablyoxygen or nitrogen.

In FIG. 6, as in the example according to FIG. 1, a fountain solution isapplied onto the hydrophilized surface of the print carrier 10 in thedampening system 18; a structuring with the aid of laser radiation 28subsequently occurs. The structured fountain solution layer is inked bythe inking system 30 and the ink is later transfer-printed onto thecarrier material 40. Ink residues are removed in the cleaning station46. Since the surface of the print carrier 10 is very smooth, just as inthe previous example, the cleaning process is simple and is to berealized with high effectiveness. The cyclical printing process cansubsequently start anew. Alternatively, a restructuring can also beomitted and the previous print image is re-inked and transfer-printed.

FIG. 7 shows the insulated electrode 72. A metallic core is surroundedby a ceramic jacket 78. In such a design, electrical arc-overs areprevented. This is primarily advantageous when metal is used as a printcarrier 10. Alternatively, the insulation can also be generated via aplastic jacket.

FIG. 8 shows the design in a print carrier 10 made from plastic. Anelectrode plate 80 is arranged on the side of the print carrier 10 thatlies opposite the electrode 72. The electrode 72 can be executed withoutinsulation.

FIG. 9 shows a hydrophilization method with an indirect coronatreatment. The output connections of the high-voltage generator 70 areconnected with two electrodes 82, 84 that are arranged above the printcarrier 10. The electrical discharges generated by the high voltagebetween the two electrodes 82, 84 generate ions that are conducted viaan air flow or process gas flow onto the surface of the print carrier 10and here deploy the wetting-aiding effect. A blower 86 is used togenerate the flow.

Alternatively, a negative pressure plasma treatment can also be usedthat increases the surface energy on the surface of the print carrier10. A high voltage discharge is hereby generated under vacuum conditions(for example in the range of 0.3 to 20 mbar), ionized by the process gasand excited into the plasma state. This plasma comes in contact with thesurface of the print carrier 10. The effect of the plasma is comparablewith the effect of the corona treatment.

A significant increase of the surface energy, which enables a very thinapplication of the frequency range fountain solution, is achieved withthe aid of the hydrophilization process specified in FIGS. 6 through 9.The layer thickness is typically in the range of 1 μm.

Various advantages result via the specified hydrophilization method. Theroughened, porous printing plate surface as in the standard offsetprinting method can be foregone. Instead of this, a very smooth surfaceis possible whose roughness range is very low, for example in a range ofthe average roughness value R_(a)<1 μm. A faster and more stablecleaning event is thereby possible for the surface. For the specifiedprinting process, neither a permanent change in the molecular or,respectively, atomic structure of the material of the print carrier nora wetting-aiding layer permanently and firmly anchored with the printcarrier is necessary. Via the specified hydrophilization process, theprint carrier can be optimized with regard to further requirementswithout consideration of the surface energy.

The specified hydrophilization process also enables the omission of thewetting-aiding additives for fountain solution used in offset printing.A further application of additional wetting-aiding substances is nolonger necessary. This prevents a relatively complicated processmanagement and reduces the additional expenses on commodities. A furtheradvantage is also in the cleaning effect of the hydrophilization method.It supports the cleaning process necessary for the digital printingmethod and thus further reduces the necessary hardware expenditure.

FIG. 10 shows a further exemplary embodiment. In offset printing and inparticular in the digital methods, for example according to U.S. Pat.No. 5,067,404 and U.S. Pat. No. 6,295,928 by the same applicant, theconstant and precisely defined thickness of the fountain solution layeron the surface of the print carrier plays a decisive role for thestability and the efficiency of the printing method. According to theexample according to FIG. 10, a print device is specified that providesand monitors a defined, controllable and regulable very thin applicationof the fountain solution. In the standardized offset printing method, adampening system is normally comprised of a number of rotating rollersused for the application of the fountain solution. Together with aroughened or porous printing plate directing good water, a water filmsufficiently stable for the standard offset printing results. Thefountain solution quantity and the thickness of the fountain solutionlayer can, for example, be adjusted via the adjustment of specificrollers relative to one another or the speed of the scoop roller. Thestorage effect of the dampening system as well as that of the printingplate hereby leads to a significantly retarded reaction to adjustmentmeasures. However, for the generation of a sufficiently stable waterfilm, the roughened, strong water-storing printing plates are absolutelynecessary. From the prior art, it is also known to generate a very thinwater film via cooling of the printing plate and the subsequentcondensation of the humidity on the printing plate. The thickness of thewater film is, however, strongly dependent on the environmentalconditions such as humidity and temperature and is hard to keep constantover longer periods of time.

In the exemplary embodiment according to FIG. 10, a design is used thatis similar to the design specified in the previously mentioned DE-A-10132 204, which realizes a CTP method (Computer-To-Press method).

The print device shown in FIG. 10 allows different print images to begenerated on the same surface of the cylindrical print carrier 10. theprint device comprises the inking system 30 with a plurality of rollersvia which oil-containing ink is transferred from the reservoir 38 ontothe surface of the print carrier 10. The inked surface of the printcarrier 10 transfers the ink onto a rubber blanket cylinder 90. Fromthere, the ink arrives on the paper web 40, which is pressed against therubber blanket cylinder 90 via the counter-pressure cylinder 42.

The dampening system 18 transfers fountain solution (for example water)via three rollers from the fountain solution reservoir 24 onto thesurface of the print carrier 10. Before the application of the fountainsolution layer, the surface of the print carrier 10 can be brought to ahydrophilic state (as this has already been specified further above)using wetting agents and/or surfactants or via a corona and/or plasmatreatment. In the further course, the fountain solution layer isselectively removed via energy supply by means of a laser beam 28 andthe desired image structure is created. As mentioned, the inking via theinking system 30 subsequently occurs on the ink-attracting regions ofthe structuring. After the structuring, the ink can be solidified bymeans of a fixing device 92.

In this example, two operating modes are also possible. In a firstoperating mode, a plurality of printing events occurs before arestructuring of the surface. The print image located on the printcarrier 10 is inked and transfer-printed once per printing, meaning amultiple inking of the print image occurs. In a second operating mode, anew print image is applied on the surface of the print carrier. Forthis, the previous structured ink-repelling layer as well as the inkresidues are to be removed, for which the cleaning station 46 isprovided. This cleaning station can be pivoted onto the print carrier 10according to the arrow P2 and pivoted away again from said print carrier10. Further details of the design of the print device according to FIG.10 are specified in the mentioned DE-A-101 32 204.

Viewed in the transport direction P1, an energy source 94 that emitsheat energy onto the fountain solution film on the surface of the printcarrier 10 is arranged after the dampening system 18. The thickness ofthe fountain solution layer is reduced with the aid of this energy.Viewed in the transport direction, a layer thickness measurement device96 is encamped after the energy source. This layer thickness measurementdevice 96 determines the current thickness of the fountain solution filmand emits an electrical signal corresponding to the thickness to acontrol 98. The control 98 compares the measured real thickness with apredetermined desired thickness. Given a desired-real value deviation,the energy source 94 is activated such that the thickness of thefountain solution layer is reduced to the desired thickness.

The layer thickness measurement device 96 can, for example, operatewithout contact according to the triangulation method, the transmissionmethod or the capacitive method. One or more IR lamps, heat radiators,laser systems, laser diodes or heating elements are suitable as energysources 94.

The cooperation of the energy source 94, the layer thickness measurementdevice 96 and the control 98 can be such that only a monitoring functionis effected. When the layer thickness undershoots or overshoots apredetermined desired value, a corresponding warning signal is emittedand the energy supply for the energy source 94 is readjusted basedthereon. The energy source 94, the layer thickness measurement device 96and the control 98 can, however, also be incorporated into a controlcircuit in which the energy source 94 is activated such that, given astandard deviation between real value and desired value of the layerthickness, this standard deviation is minimized and preferably regulatedto zero.

The energy source 94 can be activated by the control with the aid of ananalog voltage regulation or digitally via a pulse modulation, as thisis indicated by the signal series 100.

According to the example according to FIG. 10, in a first process step afountain solution film that is constant in terms of thickness isgenerated over the useable width of the print carrier 10, the fountainsolution film being reduced in terms of its layer thickness defined in asubsequent second step. The result is a uniform fountain solution layerwith defined and very slight thickness. The subsequent structuring canthus be implemented with minimal energy and with invariable result.Overall, the print quality is thus increased. The advantages of theshown print device are that an immediate reaction to a change of thelayer thickness of the fountain solution layer can ensue, that a knownand defined thickness of the fountain solution layer can be set, andthat extremely thin fountain solution layers can be generated. Thenecessary structuring energy can also be minimized, in particular fordigital printing methods.

Numerous further variations of the previously specified exemplaryembodiments are possible. For example, both a continuous band and acylinder can be used as a print carrier. The transfer printing onto thecarrier material can ensue directly or under interposition of a rubberblanket cylinder or, respectively, further intermediate cylinders for anink separation. The layer thickness regulation according to the exampleaccording to FIG. 10 can also be used for the other examples. Likewise,a fixing of the applied ink with the aid of a fixing device can occurfor the examples according to FIGS. 1 through 9. Furthermore, thecleaning station 46, the dampening system 18 and the image generationdevice can be switched to inactive and active, for example via swinging.

While a preferred embodiment has been illustrated and described indetail in the drawings and foregoing description, the same is to beconsidered as illustrative and not restrictive in character, it beingunderstood that only the preferred embodiment has been shown anddescribed and that all changes and modifications that come within thespirit of the invention both now or in the future are desired to beprotected.

1-31. (canceled)
 32. A method to generate a print image on a carriermaterial, comprising: generating a hydrophilic layer with a molecularlayer thickness at a surface of a print carrier usable for printing, asurfactant layer being applied on the surface of the print carrier togenerate the hydrophilic layer; in a structuring process, generatinghydrophilic regions and hydrophobic regions corresponding to a structureof the print image to be printed; at the surface of the print carrier,applying a fountain solution layer whereby the fountain solution layerforms only on the hydrophilic regions such that ink-attracting regionsand ink-repelling regions are created corresponding to the print imagestructure; applying on the surface ink that adheres to theink-attracting regions and that is not absorbed by the ink-repellingregions; transferring the applied ink onto the carrier material; andbefore a new structuring process, cleaning the surface of the printcarrier and regenerating a hydrophilic layer.
 33. A method according toclaim 32 wherein the hydrophilic layer on the surface of the printcarrier has a thickness of less than 100 nm.
 34. A method according toclaim 32 wherein the application of the hydrophilic layer occurs via atleast one of rolling, scraping, and spraying.
 35. A method according toclaim 32 wherein the cleaning and the regeneration of the hydrophiliclayer occurs in a single process step.
 36. A method according to claim35 wherein at least one of hot water and water vapor is used for thecleaning.
 37. A method according to claim 32 wherein radiation is usedfor the structuring.
 38. A method according to claim 37 wherein theradiation of at least one of a laser system, a laser, laser diodes, LEDsand a laser diode array is used.
 39. A method according to claim 32wherein an ink separation occurs before the transfer of the ink onto thecarrier material.
 40. A method according to claim 32 wherein the surfaceof the print carrier is one of a generated cylinder surface and acontinuous band.
 41. A device to generate a print image on a carriermaterial, comprising: a pre-treatment station via which a hydrophiliclayer with a molecular layer thickness is generated at a surface of aprint carrier usable for printing, a surfactant layer being applied onthe surface of the print carrier to generate said hydrophilic layer; animage generation station which, in a structuring process, generateshydrophilic regions and hydrophobic regions corresponding to a structureof the print image to be printed; a fountain solution applicationstation which applies a fountain solution layer on the surface of theprint carrier whereby the fountain solution layer forms only on thehydrophilic regions such that ink-attracting regions and ink-repellingregions are created corresponding to the print image structure; aninking station which applies ink that adheres to the ink-attractingregions and which is not absorbed by the ink-repelling regions; atransfer station at which the applied ink is transferred onto thecarrier material; and a cleaning station which cleans the surface of theprint carrier before a new structure process.
 42. A device according toclaim 41 wherein the hydrophilic layer on the surface of the printcarrier has a thickness of less than 100 nm.
 43. A device according toclaim 41 wherein the cleaning and a regeneration of the hydrophiliclayer occurs in a single process.
 44. A device according to claim 41wherein radiation is used for the structuring.
 45. A device according toclaim 44 wherein the radiation of at least one of a laser system, alaser, laser diodes LEDs and a laser diode array is used.
 46. A deviceaccording to claim 41 wherein an ink separation occurs before thetransfer of the ink onto the carrier material.
 47. A device according toclaim 41 wherein the surface of the print carrier is one of a generatedcylinder surface and a continuous band.
 48. A method to generate a printimage on a carrier material, comprising the steps of: providing asurface of the print carrier with an S_(i)O₂ layer and a hydrophiliclayer with a molecular layer thickness and comprising S_(i)OH moleculesvia hot water vapor; in a structuring process, generating hydrophilicregions and hydrophobic regions corresponding to a structure of theprint image to be printed; at the surface of the print carrier, applyinga fountain solution layer whereby the fountain solution layer forms onlyon the hydrophilic regions such that ink-attracting regions andink-repelling regions are created corresponding to the structuring;applying on the surface ink that adheres to the ink-attracting regionsand that is not absorbed by the ink-repelling regions; transferring theapplied ink onto the carrier material; and before a new structuringprocess, cleaning the surface of the print carrier and regenerating ahydrophilic layer.
 49. A method according to claim 48 wherein thehydrophilic layer on the surface of the print carrier has a thickness ofless than 100 nm.
 50. A method according to claim 48 wherein thecleaning and the regeneration of the hydrophilic layer occurs in asingle process step.
 51. A method according to claim 50 wherein at leastone of hot water and water vapor is used for the cleaning.
 52. A methodaccording to claim 48 wherein radiation is used for the structuring. 53.A method according to claim 52 wherein the radiation of at least one ofa laser system, a laser, laser diodes, LEDs and a laser diode array isused.
 54. A method according to claim 48 wherein an ink separationoccurs before the transfer of the ink onto the carrier material.
 55. Amethod according to claim 48 wherein the surface of the print carrier isone of a generated cylinder surface and a continuous band.
 56. A deviceto generate a print image on a carrier material, comprising: apre-treatment station with which an S_(i)O₂ layer and a hydrophiliclayer with a molecular layer thickness is generated on a surface of aprint carrier usable for printing; an image generation station which, ina structuring process, generates hydrophilic regions and hydrophobicregions corresponding to a structure of the print image to be printed;an application station which applies a fountain solution layer on thesurface of the print carrier whereby the fountain solution layer formsonly on the hydrophilic regions such that ink-attracting regions andink-repelling regions are created corresponding to the print imagestructure; an inking station which applies on the surface ink thatadheres to the ink-attracting regions and which is not absorbed by theink-repelling regions; a transfer station at which the applied ink istransferred onto the carrier material; and a cleaning station whichcleans the surface of the print carrier before a new structure process.57. A device according to claim 56 wherein the hydrophilic layer on thesurface of the print carrier has a thickness of less than 100 nm.
 58. Adevice according to claim 56 wherein the cleaning and the a regenerationof the hydrophilic layer occurs in a single process step.
 59. A deviceaccording to claim 56 wherein radiation is used for the structuring. 60.A device according to claim 59 wherein the radiation of at least one ofa laser system, a laser, laser diodes, LEDs and a laser diode array isused.
 61. A device according to claim 56 wherein an ink separationoccurs before the transfer of the ink onto the carrier material.
 62. Adevice according to claim 56 wherein the surface of the print carrier isone of a generated cylinder surface and a continuous band.
 63. A methodto generate a print image on a carrier material, comprising: generatinga hydrophilic layer at a surface of a print carrier usable for printing,a surfactant layer being applied on the surface of the print carrier togenerate the hydrophilic layer; in a structuring process, generatinghydrophilic regions and hydrophobic regions corresponding to a structureof the print image to be printed; at the surface of the print carrier,applying a fountain solution layer whereby the fountain solution layerforms on the hydrophilic regions such that ink-attracting regions andink-repelling regions are created corresponding to the print imagestructure; applying on the surface ink that adheres to theink-attracting regions and that is not substantially absorbed by theink-repelling regions; transferring the applied ink onto the carriermaterial; and before a new structuring process, cleaning the surface ofthe print carrier.
 64. A device to generate a print image on a carriermaterial, comprising: a pre-treatment station via which a hydrophiliclayer is generated at a surface of a print carrier usable for printing,a surfactant layer being applied on the surface of the print carrier togenerate said hydrophilic layer; an image generation station which, in astructuring process, generates hydrophilic regions and hydrophobicregions corresponding to a structure of the print image to be printed; afountain solution application station which applies a fountain solutionlayer on the surface of the print carrier whereby the fountain solutionlayer forms on the hydrophilic regions such that ink-attracting regionsand ink-repelling regions are created corresponding to the print imagestructure; an inking station which applies ink that adheres to theink-attracting regions and which is not absorbed by the ink-repellingregions; a transfer station at which the applied ink is transferred ontothe carrier material; and a cleaning station which cleans the surface ofthe print carrier.
 65. A method to generate a print image on a carriermaterial, comprising the steps of: providing a surface of the printcarrier with an S_(i)O₂ layer and a hydrophilic layer comprising S_(i)OHmolecules via hot water vapor; in a structuring process, generatinghydrophilic regions and hydrophobic regions corresponding to a structureof the print image to be printed; at the surface of the print carrier,applying a fountain solution layer whereby the fountain solution layerforms only on the hydrophilic regions such that ink-attracting regionsand ink-repelling regions are created corresponding to the structuring;applying on the surface ink that adheres to the ink-attracting regionsand that is not absorbed by the ink-repelling regions; transferring theapplied ink onto the carrier material; and before a new structuringprocess, cleaning the surface of the print carrier.
 66. A device togenerate a print image on a carrier material, comprising: apre-treatment station with which an S_(i)O₂ layer and a hydrophiliclayer is generated via a hot water vapor on a surface of a print carrierusable for printing; an image generation station which, in a structuringprocess, generates hydrophilic regions and hydrophobic regionscorresponding to a structure of the print image to be printed; anapplication station which applies a fountain solution layer on thesurface of the print carrier whereby the fountain solution layer formson the hydrophilic regions such that ink-attracting regions andink-repelling regions are created corresponding to the print imagestructure; an inking station which applies on the surface ink thatadheres to the ink-attracting regions and which is not absorbed by theink-repelling regions; a transfer station at which the applied ink istransferred onto the carrier material; and a cleaning station whichcleans the surface of the print carrier.